The tumor necrosis factor (TNF-alpha) regulates many biological activities, including immune responses, inflammation and programmed cell death (apoptosis). TNF-alpha exerts its function by activating multiple intracellular signaling effectors, such as caspases, NF-kappaB and c-Jun N-terminal protein kinase (JNK). While caspase activation is required for TNF-alpha induced apoptosis, activation of NF-kappaB suppresses the apoptotic process. The role of JNK in TNF-alpha induced apoptosis is unclear. Using genetic and biochemical approaches, we found that activation of NF-kappaB prevents prolonged JNK activation induced by TNF-alpha through induction of a group of inhibitors. Inhibition of prolonged JNK activation suppresses TNF-alpha induced apoptosis, suggesting that part of the anti-apoptotic effect of NF-kappaB is mediated by inhibition of prolonged JNK activation. This work is novel as it provides evidence that will lead to delineation of the molecular basis of how TNF-alpha signaling is integrated in the apoptotic process and should provide information critical to the development of novel strategies in regulation of TNF-alpha induced apoptosis. Two hypothesis-driven specific aims will be pursued to determine the mechanisms by which activation of NF-kappaB prevents prolonged JNK activation in response to TNF-alpha and the mechanism by which prolonged JNK activation contributes to TNF-alpha induced apoptosis.